Carbon molecular sieves are porous substrates with an open-network structure of controlled molecular dimension used to separate small molecular gases or liquids from larger molecular sized gases or liquids based on differences in capacity or rates of adsorption. See for example, Grant, U.S. Pat. No. 3,884,830 and references cited therein.
Carbon molecular sieves have generally been prepared in an externally fired rotary kiln or other similar non-continuous, batch-type furnace. One such batch-type manufacturing process is described in U.S. Pat. No. 3,979,330. Coke combined with pitch, bitumen, tar or tar oil is heated at from 600.degree. to 900.degree. C. and then subjected to carbon splitting off atmosphere at this temperature for a prolonged period. The carbon splitting atmosphere causes carbon deposits to be formed, adjusting the average pore diameter of the cokes. If the coke combined with pitch, bitumen, tar or tar oil is heated from 600.degree. to 900.degree. C. and the coking products are not separated off with a rinsing or scavenger gas, the gas-formed coking product will exert the same effect as the carbon splitting off hydrocarbon. See also, Great Britain Patent Specification No. 1,181,209.
The major difficulties associated with the batch-type noncontinuous manufacture of carbon molecular sieves are (1) the need for painstaking atmospheric and temperature regulation for the control of the pore diameter; (2) the product variability from batch to batch, i.e., quality control; and (3) relatively long residence time. See Munzner et al. U.S. Pat. No. 3,962,129.
The use of a continuous transport type heating means and a cocurrent inert purge gas, as described herein, eliminates the difficulties of atmosphere and temperature control and relatively long residence times associated with prior art batch-type processing.